CT-derived visceral adiposity and paraspinal muscle depletion associated with severe acute pancreatitis according to the Revised Atlanta Classification.

PURPOSE: To evaluate whether CT-derived visceral adiposity and skeletal muscle metrics are associated with severe acute pancreatitis (AP), as defined by the Revised Atlanta Classification, in a selected cohort of CT-imaged patients. METHODS: This retrospective study included 254 adults with AP who underwent abdominal CT and had follow-up imaging. Mild and moderately severe AP were combined as the non-severe group and compared with severe AP. Visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), bilateral erector spinae and psoas muscle areas, and muscle attenuation were measured at L3 on the earliest available unenhanced CT series. ROC analysis with exploratory Youden cutoffs, DeLong tests, bootstrap internal validation, and age- and sex-adjusted logistic regression were performed. RESULTS: The cohort included 198 non-severe and 56 severe AP cases. Severe AP was associated with higher VAT and SAT areas and lower muscle area and attenuation. VAT outperformed SAT (AUC 0.810 vs. 0.645; p = 0.00048), and erector spinae area outperformed psoas area (AUC 0.923 vs. 0.870; p = 0.0086). VAT (OR 4.88 per 5,000 mm² increase; p < 0.001) and erector spinae area (OR 2.71 per 1,000 mm² decrease; p < 0.001) remained independently associated with severe AP. CONCLUSION: CT-derived VAT and erector spinae muscle area were independently associated with Revised Atlanta-defined severe AP. These opportunistic imaging biomarkers may complement, rather than replace, clinical risk stratification, and the proposed thresholds require external validation.